The support of access to STA-selected APs is a general requirement in any wireless system where the mobile stations access the network through APs or base stations, and for many real time based applications, any delay in the access process may degrade the quality of the service. The problem of minimizing the access delay remains a major challenge for most wireless system designers. One of the main issues is the limited ability of the mobile stations in discovering and maintaining network state information for use in optimization of the AP selection procedure. This problem is compounded by the STAs' need to have information about the service providers supported by an AP and/or neighboring APs in choosing an AP to access.
Handoffs between wireless local area networking (WLAN) technologies and cellular technologies such as 2G/3G/4G GSM, CDMA, TDMA etc., are taking on increasing significance because connectivity through WLANs increases cellular coverage area. It is also attractive since WLAN technologies are un-licensed thus have: 1) low cost; 2) the potential to provide higher data rates; and 3) ability to provide quality of service (QoS) for multimedia applications.
In IEEE 802.11 wireless networks, information about neighboring APs and the service providers supported is included in beacons, which are transmitted at least at one of fixed and predetermined intervals of time as well as in probe responses and measurement reports. The measurement reports can be initiated by request from a STA or they can be generated autonomously. Furthermore, some other channels being used by neighboring APs, AP capability and supported service provider information can be conveyed to STAs in response to probe requests.
The information about SPs helps a STA to find an SP through an AP for handover or to establish a connection through a WLAN without any prior connection in less time. The information about neighbor APs operating in other channels helps a STA minimize the time it takes the STA to locate a candidate AP for roaming Reducing roaming delay is fundamental to lessen packet losses and support seamless connectivity, which is a key requirement for several applications like video, voice, critical patient monitoring including legacy data applications.
According to the proposed methods in the IEEE 802.11k draft D2.0 amendment, an AP can transmit a list of valid channels and a list of APs in its neighborhood along with some of their capabilities to help STAs to find a candidate AP for roaming. Though this information helps a STA to not arbitrarily scan channels or to look for APs that may not have the capabilities the STA expects, the list may have more than one channel or neighbor AP indicated which may increase scanning delay to find the right AP candidate to roam to. Thus, a STA would have to switch to each channel in the list and/or inquire each AP in the neighbor report element via probe request or via some other measurements such as received signal strength to find the right AP.
According to the proposed methods in the IEEE 802.11 TGu, an AP can transmit a list of SPs along with some of their capabilities to help STAs find a suitable SP to connect to. Though this information helps a STA to not inquire of an AP for one or more SPs that it could/would want to connect to, the list may have more than one SP, and, therefore, a STA would have to look at additional parameters such as the associated costs, the communication parameters, the security/authentication parameters, the type of service supported, etc., to select an SP to connect to. A complete list of all possible parameters of interest to STAs would use prohibitively large communication frames and time, thus reducing the efficiency of the communication protocol for data transmission.
Thus, there is a need in the art to describe the relative merits of the APs and SPs in a compact manner, for example, due to associated costs, level of integration of the AP services with the SP's, priority assigned to the traffic coming from and going to the SP, priority assigned by the AP to honor requests for connection with a particular SP, number and types of services offered when connected to a particular SP, etc. This need includes a need in the art to lessen the time to find the right channel and/or AP amongst the neighbor APs or amongst the regulatory valid channels, and/or to find the right SP to connect to.